Topiramate

Topiramate is an anticonvulsant medication approved for the treatment of partial-onset seizures in adults and children and for the preventive treatment of migraine in adults (and some adolescents). It is also marketed in combination with phentermine for weight management under the brand name Qsymia. The drug is available in oral tablets and sprinkle capsules, allowing dosing adjustments and use in patients who have difficulty swallowing.

The exact mechanism of topiramate is not fully understood. It is believed to act through multiple pathways, including inhibition of voltage-gated sodium channels, enhancement of gamma-aminobutyric acid (GABA)–mediated activity, antagonism of excitatory AMPA/kainate receptors, and inhibition of certain carbonic anhydrase enzymes. This combination of actions contributes to its anticonvulsant effects and may influence its impact on migraine and other conditions.

Dosing is individualized and typically adjusted gradually to minimize side effects. For epilepsy, maintenance doses are commonly titrated over several weeks. For migraine prevention, lower initial doses are often increased to an effective level as tolerated. Topiramate is generally taken orally, with or without food. It is supplied as tablets and sprinkle capsules.

Common adverse effects include cognitive effects (such as attention and concentration difficulties), somnolence, dizziness, paresthesias, and weight loss. Less frequent but important risks are metabolic acidosis, kidney stone formation, reduced sweating, and, rarely, acute myopia or secondary angle-closure glaucoma. There is also an increased risk of birth defects if used during pregnancy, particularly orofacial clefts; women of childbearing potential should use effective contraception and discuss risks with a clinician. Caution is advised in patients with renal impairment, and gradual discontinuation is recommended to reduce the risk of seizures. Patients should be monitored for mood changes and suicidal thoughts.